One type of nonlinear optical frequency conversion device utilizes the phenomenon of optical parametric amplification in which energy provided at one wavelength in a “pump” optical signal is converted into energy at two other wavelengths of waves commonly referred to as “signal” and “idler” waves. For example, one type of optical parametric amplification (OPA) device employs so-called “quasi-phase matched” (QPM) techniques to produce a phase-matched optical parametric oscillator (OPO) output in the ultraviolet/visible, near infrared or midwave infrared (MWIR) spectral range. QPM devices produce phase-matched output by resetting the phase mismatch of the three optical signals by π radians every “coherence length”, which for MWIR OPOs may be in the range of 20-40 microns. One method of resetting the phase mismatch is accomplished by anti-parallel domains of electric polarization that alternate in sign every coherence length. Current QPM technology uses ferroelectric crystals (the electric analogue of a ferromagnet where there is a permanent electric moment along a preferred direction) within which a modulated electric domain structure is induced using a photo-lithographically fabricated periodic electrodes. Very high field strengths, such as in the range of 2-20 kV/mm, are utilized to obtain the desired operation. The term “periodic poling” (PP) is used to describe this kind of QPM fabrication.
Current PP QPM technology is limited to crystal structures with thicknesses in the range of 1-5 mm. This limit is imposed by the fundamental dielectric breakdown strength of the ferroelectric crystals. This thickness limitation poses a potentially serious constraint on the utility of PP QPM structures for use in OPOs or other nonlinear frequency converters that are used to generate high pulse energy output. The limitation is based on the fact that the limited cross sectional area A of the QPM device (approx. 0.1-0.3 cm2) restricts both the maximum pump pulse energy and output pulse energy to a value imposed by a product (F*A) of the cross sectional area A and an optical damage limit F for a typical QPM device, which may be in the range of F=3-10 J/cm2 for example.